Which of the following is an intervention the exchange can carry out?

• A. Delay opening of trading in a security
• B. Increase margin requirements unilaterally
• C. Prohibit all trading of a security permanently
• D. Change ticker symbols mid-session

Answer: (A)

Interventions by an exchange are actions taken to keep trading orderly when information is pending or systems are being fixed. Delaying the opening of trading in a security is a real mechanism an exchange can use to prevent a chaotic start and to ensure participants have a fair chance to access relevant information. The other options don’t reflect standard exchange powers: margins are governed by the clearinghouse and regulators, not something the exchange would unilaterally raise; prohibiting all trading permanently would go beyond typical authority and would require regulatory action; changing ticker symbols mid-session would cause confusion and is not a permissible market intervention.